Effects of dopant materials on the characteristics of the nano-sized Co₃O₄ powders prepared by spray pyrolysis

Pure and M-doped Co₃O₄ (M = Cr, Fe, Mg, Zr) powders with a nanometre size and a narrow size distribution were prepared by spray pyrolysis from a spray solution with citric acid and ethylene glycol. The precursor powders with a hollow and thin walled structure were turned to nano-sized Co₃O₄ powders after post-treatment. The mean size of the pure Co₃O₄ powders post-treated at a temperature of 600°C was 77 nm. On the other hand, the mean sizes of the doped Co₃O₄ powders with a doping concentration of 3 mol.% were changed from 24 to 63 nm. The Mg-doped Co₃O₄ powders had the minimum mean size. The mean sizes of the Mg-doped Co₃O₄ powders with doping concentrations of 1 and 5 mol.% were 60 and 61 nm. The mean sizes of the Mg-doped Co₃O₄ powders with a doping concentration of 3 mol.% post-treated at temperatures of 700 and 800°C were 63 to 102 nm.